Spring Framework

1
Spring Framework
2
Agenda

• What is Spring?
• Loose coupling with Dependency Injection
• Declarative programming with AOP
• Eliminating Boilerplate with templates

3
What is Spring?
4
What is Spring?

• Lightweight container framework
• Lightweight - minimally invasive
• Container - manages app component lifecycle
• Framework - basis for enterprise Java apps
• Open source
• Apache licensed

5
What its not

• An application server
• Although...theres tcServer, dmServer
• And Spring supports a lot of the EJB3 model

6
The Spring Way

• Springs overall theme Simplifying Enterprise
  Java Development
• Strategies
• Loose coupling with dependency injection
• Declarative programming with AOP
• Boilerplate reduction with templates
• Minimally invasive and POJO-oriented

7
A brief history of Spring

• Spring 1.0
• DI, AOP, web framework
• Spring 2.0
• Extensible config, bean scoping, dynamic language
  support, new tag library
• Spring 2.5
• Annotation-driven, automatic bean discovery, new
  web framework, JUnit 4 integration
• Spring 3.0
• REST, SpEL, declarative validation, ETag support,
  Java-based configuration

8
Beyond the framework

• Spring Web Flow
• BlazeDS Integration
• Spring-WS
• Spring Security
• Spring-DM
• dmServer
• Bundlor
• tcServer

• Spring Batch
• Spring Integration
• Spring LDAP
• Spring IDE / STS
• Spring Rich Client
• Spring .NET
• Spring BeanDoc
• Groovy/Grails

9
Spring community

• Forum http//forum.springframework.org
• Issues http//jira.springframework.org
• Extensions
• http//www.springframework.org/extensions
• Conferences, user groups, etc
• GET INVOLVED!

10
Loose CouplingwithDependency Injection
11
Whats wrong here?

• public class Mechanic
• public void fixCar()
• PhillipsScrewdriver tool
• new PhillipsScrewdriver()
• tool.use()

12
How about now?

• public class Mechanic
• public void fixCar()
• Tool tool
• new PhillipsScrewdriver()
• tool.use()

13
Any better?

• public class Mechanic
• public void fixCar()
• ToolFactory tf
• ToolFactory.getInstance()
• Tool tool tf.getTool()
• tool.use()

14
Certainly this is better...

• public class Mechanic
• public void fixCar()
• InitialContext ctx null
• try
• ctx new InitialContext()
• Tool quest (Tool) ctx.lookup(
• "javacomp/env/Tool")
• tool.use()
• catch (NamingException e)
• finally
• if(ctx ! null)
• try ctx.close()
• catch (Exception e)

15
Lets try again...

• public class Mechanic
• private Tool tool
• public Mechanic(Tool tool)
• this.tool tool
• public void fixCar()
• tool.use()

16
Or maybe this...

• public class Mechanic
• private Tool tool
• public void setTool(Tool tool)
• this.tool tool
• public void fixCar()
• tool.use()

17
Dependency injection

• Objects are given what they need
• Coupling is low when used with interfaces
• Makes classes easier to swap out
• Makes classes easier to unit test

18
DI in Spring

• Several options
• XML
• Annotation-driven
• Java-based configuration
• None are mutually exclusive

19
XML-based wiring

• ltbean id"screwdriver"
• class"com.habuma.tools.PhillipsScrewdriver"
  /gt
• ltbean id"mechanic"
• class"com.habuma.mechanic.AutoMechanic"gt
• ltconstructor-arg ref"screwdriver" /gt
• lt/beangt

ltbean id"screwdriver" class"com.habuma.tools
.PhillipsScrewdriver" /gt ltbean id"mechanic"
class"com.habuma.mechanic.AutoMechanic"gt
ltproperty name"tool" ref"screwdriver"
/gt lt/beangt
20
Annotation-based wiring
ltcontextcomponent-scan base-package"com.habu
ma.mechanic" /gt
public class Mechanic private Tool
tool _at_Autowired public void setTool(Tool tool)
this.tool tool public void
fixCar() tool.use()

• public class Mechanic
• _at_Autowired
• private Tool tool
• public void fixCar()
• tool.use()

21
Java-based configuration

• _at_Configuration
• public class AutoShopConfig
• _at_Bean
• public Tool screwdriver()
• return new PhillipsScrewdriver()
• _at_Bean
• public Mechanic mechanic()
• return new AutoMechanic(screwdriver())

22
Declarative Programming with AOP
23
Aspects

• Separate loosely-related behavior
• Objects dont have to do work that isnt their
  job
• Keeps them cohesive
• Keeps them simple

24
Life without AOP

• public void withdrawCash(double amount)
• UserTransaction ut context.getUserTransaction
  ()
• try
• ut.begin()
• updateChecking(amount)
• machineBalance - amount
• insertMachine(machineBalance)
• ut.commit()
• catch (ATMException ex)
• LOGGER.error("Withdrawal failed")
• try
• ut.rollback()
• catch (SystemException syex)
• // ...

25
Life with AOP

• public void withdrawCash(double amount)
• try
• updateChecking(amount)
• machineBalance - amount
• insertMachine(machineBalance)
• catch (ATMException ex)
• LOGGER.error("Withdrawal failed")

26
With some more AOP

• public void withdrawCash(double amount)
• updateChecking(amount)
• machineBalance - amount
• insertMachine(machineBalance)

27
Spring AOP

• Comes in 3 forms
• XML-based
• Annotation-based
• Native AspectJ

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AOP Terms

• Aspect
• Advice
• Pointcut
• Joinpoint

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Logging aspect

• public class LoggingAspect
• private static final Logger LOGGER
• Logger.getLogger(LoggingAspect.class)
• public logBefore()
• LOGGER.info("Starting withdrawal")
• public logAfterSuccess()
• LOGGER.info("Withdrawal complete")
• public logFailure()
• LOGGER.info("Withdrawal failed")

30
XML-based AOP

• ltbean id"loggingAspect"
• class"LoggingAspect" /gt
• ltaopconfiggt
• ltaopaspect ref"loggingAspect"gt
• ltaopbefore
• pointcut"execution( .withdrawCash(..))"
  
• method"logBefore" /gt
• ltaopafter-returning
• pointcut"execution( .withdrawCash(..))"
  
• method"logBefore" /gt
• ltaopafter-throwing
• pointcut"execution( .withdrawCash(..))"
  
• method"logBefore" /gt
• lt/aopaspectgt
• lt/aopconfiggt

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Annotation-based AOP

• _at_Aspect
• public class LoggingAspect
• private static final Logger LOGGER
• Logger.getLogger(LoggingAspect.class)
• _at_Pointcut("execution( .withdrawCash(..))")
• public void withdrawal()
• _at_Before("withdrawal()")
• public logBefore()
• LOGGER.info("Starting withdrawal")
• _at_AfterReturning("withdrawal()")
• public logAfterSuccess()
• LOGGER.info("Withdrawal complete")
• _at_AfterThrowing("withdrawal()")
• public logFailure()
• LOGGER.info("Withdrawal failed")

ltaopaspectj-autoproxy /gt
32
What about transactions?

• lttxadvice id"txAdvice"gt
• lttxattributesgt
• lttxmethod name"withdraw"
• propagation"REQUIRED" /gt
• lttxmethod name"inquire"
• propagation"SUPPORTS"
• read-only"true" /gt
• lt/txattributesgt
• lt/txadvicegt

33
Annotating transactions

• lttxannotation-driven /gt

_at_Transactional(propagationPropagation.REQUIRED) p
ublic void withdrawCash(double amount)
updateChecking(amount) machineBalance -
amount insertMachine(machineBalance)
_at_Transactional(propagationPropagation.SUPPORTS,
readOnlytrue) public double inquireBalance(Stri
ng acctNo) // ...
34
Eliminating BoilerplatewithTemplates
35
Boilerplate

• Exists everywhere
• JDBC
• JNDI
• JMS
• ...all over JEE...
• Lots of plumbing code repeated over and over

36
Recognize this?

• public void addSpitter(Spitter spitter)
• Connection conn null
• PreparedStatement stmt null
• try
• conn dataSource.getConnection()
• stmt conn.prepareStatement(SQL_INSERT_SPIT
  TER)
• stmt.setString(1, spitter.getUsername())
• stmt.setString(2, spitter.getPassword())
• stmt.setString(3, spitter.getFullName())
• stmt.execute()
• catch (SQLException e)
• // do something...not sure what, though
• finally
• try
• if (stmt ! null)
• stmt.close()
• if (conn ! null)
• stmt.close()

37
Ring any bells?

• InitialContext ctx null
• try
• ctx new InitialContext()
• DataSource ds (DataSource) ctx.lookup(
• "javacomp/env/jdbc/Spitt
  erDatasource")
• catch (NamingException ne)
• // handle naming exception
• finally
• if(ctx ! null)
• try
• ctx.close()
• catch (NamingException ne)

38
Get the message?

• ConnectionFactory cf
• new ActiveMQConnectionFactory("tcp//localhost
  61616")
• Connection conn null
• Session session null
• try
• conn cf.createConnection()
• session conn.createSession(false,
  Session.AUTO_ACKNOWLEDGE)
• Destination destination new
  ActiveMQQueue("myQueue")
• MessageProducer producer session.createProduce
  r(destination)
• TextMessage message session.createTextMessage(
  )
• message.setText("Hello world!")
• producer.send(message)
• catch (JMSException e)
• finally
• try
• if(session ! null) session.close()
• if(conn ! null) conn.close()
• catch (JMSException ex)

39
JDBC template
ltbean id"dataSource"
class"org.springframework.jdbc.datasource.DriverM
anagerDataSource"gt ltproperty
name"driverClassName" value"db.driver" /gt
ltproperty name"url" value"db.url" /gt
ltproperty name"username" value"db.username"
/gt ltproperty name"password"
value"db.password" /gt lt/beangt
ltbean id"jdbcTemplate"
class"org.springframework.jdbc.core.simple.Simple
JdbcTemplate"gt ltconstructor-arg
ref"dataSource" /gt lt/beangt ltbean
id"spitterDao" class"com.habuma.spitter
.persistence.SimpleJdbcTemplateSpitterDao"gt
ltproperty name"jdbcTemplate" ref"jdbcTemplate"
/gt lt/beangt

• public void addSpitter(Spitter spitter)
• jdbcTemplate.update(SQL_INSERT_SPITTER,
• spitter.getUsername(),
• spitter.getPassword(),
• spitter.getFullName())
• spitter.setId(queryForIdentity())

40
Spring-flavored JNDI

• ltjeejndi-lookup id"dataSource"
• jndi-name"jdbc/SpitterDatasource"
• resource-ref"true" /gt

41
Spring-flavored JNDI

• ltbean id"jmsTemplate"
• class"org.springframework.jms.core.JmsTemplat
  e"gt
• ltproperty name"connectionFactory"
  ref"connectionFactory" /gt
• lt/beangt

public void sendMotoristInfo(final Motorist
motorist) jmsTemplate.send(destination,
new MessageCreator()
public Message createMessage(Session session)
throws JMSException
MapMessage message session.createMapMessage()
message.setString("lastName",
motorist.getLastName())
message.setString("firstName", motorist.getFirstNa
me()) message.setString("email",
motorist.getEmail()) return message
)
42
Summary
43
Spring...

• Is a lightweight container framework
• Simplifies Java development
• POJO-oriented
• Promotes loose coupling with dependency injection
• Supports declarative programming with AOP
• Eliminates boilerplate code with templates

44
Where were headed next

• Spring 3 without XML and the ADD developer
• Building web applications with Spring _at_MVC
• Spring JPA Hibernate
• Spring Security
• Grails
• Spring-DM
• Panel discussion